1. Field of the Invention
The invention relates to a process for continuously producing a glassy or vitrified blast furnace slag, in which the slag is applied onto a cooling roll or onto articulately interlinked cooling plates conducted as an endless conveyor belt over deflection pulleys and wherein cooling of the slag is effected dry, as well as an arrangement for carrying out the process.
The invention, in particular, aims at providing an efficient process by which the subsequent dry granulation of blast furnace slag is feasible at operating costs as low as possible while saving the environment to the largest extent possible.
2. Prior Art
Usual processes for granulating blast furnace slag, for instance in view of further processing in the cement industry, at present are devised as wet processes. The liquid blast furnace slag is united with large amounts of water, thereby solidifying to glassy granulates. In doing so, the total heat content is destroyed and SO.sub.2 and H.sub.2 S are usually formed, wherein, to make things worse, sulphur-containing waste waters are formed, the disposal of which involves additional expenditures.
From DE 29 50 974 A, an arrangement for the production of a glassy or vitrified blast furnace slag is known, in which an endless conveyor belt is provided with cooling grooves extending on the external surface and narrowing towards the groove roots. Via a slag melt vessel, slag melt is filled into the cooling grooves and, after cooling and solidification, is ejected from the cooling grooves on a predetermined site by means of a scraper provided on the internal surface of the conveyor belt.
From AT B 380 490 an arrangement for recovering the sensible heat of dumpable hot material may be taken, such an arrangement being intended for cooling, in particular, liquid blast furnace slag while recovering the sensible heat.
The known arrangement comprises an endless conveyor belt conducted over at least two deflection pulleys and formed of articulately interlinked plates, on the upper half of which conveyor belt the hot material is applied, the empty lower half of the conveyor belt being conducted through a cooling zone. With such a dry cooling, the high cooling speed required for vitrification without involving the risk of subsequent crystallization or recrystallization usually cannot be readily realized. For that reason, such known arrangements are frequently operated primarily with a view to as complete a recovery of energy as possible during cooling, thus accepting subsequent crystallization or recrystallization.
The known arrangement is applicable, in particular, also for hot material that must be cooled while avoiding the access of air such as, for instance, in the dry quenching of coke.
The known arrangement comprises a plurality of cooling plates, the cooling plates in the upper half being appropriately heated and in the lower half cooperating with cooling devices, which may be formed, for instance, by cooling plates through which a coolant flows. Heat transfer in that arrangement is effected by radiation or by the immediate contact of the counter cooling plates of the conveyor belt with the cooling plates for the purpose of cooling the cooling plates of the conveyor belt. The cooling device may also be formed by consecutively arranged holler counter cooling plates, wherein the upper sides of such counter cooling plates may be designed as smooth sliding surfaces getting into contact with the cooling plates of the conveyor belt.